Turbine driven pop-up sprinkler heads of the type shown in my U.S. Pat. No. 2,909,325 provided a step increase in the art of irrigation. Previously, rotary sprinklers were of the impact driven type wherein a high velocity stream of water deflected a spring-loaded hammer which nudged the sprinkler in a rotary direction about a vertical pin-axis upon its return. Whereas such impact driven sprinklers emitted a high precipitation rate water stream in order to effect the necessary forces to cause rotation, the pop-up type sprinklers of my aforementioned patent employed a small water turbine wheel rotating at relatively high speed to effect slow rotation of a sprinkler nozzle turret on top. Accordingly, the emitted stream or streams of water from one or more nozzle openings in the rotating turret could be such as to effect a low precipitation rate of water dispersal to maximize water penetration to the desired area while minimizing undesired water runoff.
In my later issued U.S. Pat. No. 3,854,664, I disclosed improvements to such turbine driven sprinklers. In particular, a bulkhead was disposed between the common source of water under pressure and the plurality of nozzle openings contained in a rotating turret. Each of the nozzles terminated in an opening wiping over the surface of the bulkhead as the turret turned. By providing openings in the bulkhead, the pathways to the nozzles were selectively opened and shut as a function of the direction in which the particular is instantaneously facing. In this manner, a preestablished on/off spray pattern was put into the sprinkler head. However, the preestablished pattern was limited to circular arcs.
In pattern sprinklers, a rectangular shape is very often desirable, as most garden and landscape areas are on rectangular lots surrounding rectangular buildings. Known sprinkler heads creating a rectangular spray pattern are of the fixed and oscillating type. The fixed type, having a plurality of holes in the top, generally does not distribute water evenly over the entire area and tends to be of a high precipitation rate type. The oscillating type is large and is generally not suited to the permanent irrigation systems, but rather to connection to the end of a garden-type hose for selective placement within an area to be watered on a time-by-time basis.
Furthermore, in those prior art sprinklers capable of watering a preestablished pattern, the size of the pattern is changed by an increasing or decreasing the pressure of the water supplied to the sprinkler. By doubling the pressure, the area coverable by the prior art sprinklers increases by approximately four times. However, the gallonage discharged by the sprinkler nozzles only increases by a factor of 1.41 (the square root of 2). Accordingly, the precipitation rate is greatly reduced when the prior art sprinklers are used to cover a larger area by increasing the pressure of the water supplied to the sprinklers.
Accordingly, it is the primary object of the present invention to discharge water from a sprinkler head over a preselected pattern at a constant precipitation rate.